Group 'Other' items not in the 'Top 5' (XP)

(Edited by HansV to format data as table)

This is probably simple for many of you, but not only can I not accomplish it on my own, I have not been able to find a reference to this in archives.
For the sake of argument, assume I have a field called "ItemName" in a table, that contains a few hundred records and there 15 or so unique item names in the ItemName field. I want a report that shows the Top 5 Item Names sold with the count and percentage (easy part) PLUS a category "Other" that contains the count all remaining records that are not included in the Top 5. How is this accomplished?
Example:

Re: Group 'Other' items not in the 'Top 5' (XP)

Hans,

The first two queries work like fine clockwork. However, the second results in the following error message:
“The ORDER BY expression (Sort) includes fields that are no selected by the query. Only those fields requested in the first query can be included in an ORDER BY expression.”

When I remove the Sort from the ORDER BY it does run, but uputs the "Other" into the mix, instead of last.
The queries:
1 No Problems with this executing.
SELECT TOP 5 ItemName, Count(*) AS Num, 1 AS Sort
FROM tblInventory
GROUP BY ItemName
ORDER BY Count(*) DESC;

2. No problem with this one executing
SELECT "Other" AS ItemName, Count(*) AS Num, 2 AS Sort
FROM tblInventory
WHERE (((ItemName) Not In (SELECT ItemName FROM sqTop5)));

3. Problem only when I include the "ORDER BY Sort, "
SELECT ItemName, Num FROM sqTop5
UNION SELECT ItemName, Num FROM sqOtherCauses
ORDER BY Sort, Num DESC;

4. Same as above sans "ORDER BY Sort". Like this it runs, however, without the Sort included I don't have access to the "1" and "2" created in the first two select queries.
SELECT ItemName, Num FROM sqTop5
UNION SELECT ItemName, Num FROM sqOtherCauses
ORDER BY Num DESC;

What am I overlooking?

Also, my first post stated "a few hundred" records and should have been "thousands". I executed and timed the second query six times each for 1000, 2000, 3000, and 4000 records. The second query average times are 4 seconds, 14.4 seconds, 33 seconds and 58.8 seconds when run against 1000, 2000, 3000 and 4000 records respectively. The machine specs are:
Pentium 4, 2.8 mhz, 512 meg RAM, XP Home Edition and Access XP the only app running. From 2000 to 3000 and 3000 to 4000 the times are doubling for each addition of 1000 records. Is that to be expected?